Continued efforts have been made to determine the etiological agents associated with Multiple Sclerosis. We have continued to use the direct migration inhibition, lymphocyte cytotoxicity and complement mediated cytotoxic tests to determine the cellular immune response of MS patients and carefully matched controls. We have developed a technique associated with flow cytofluorometry to measure responses in a small number of lymphocytes in an effort to determine the cellular immune response in cerebrospinal fluid cells. We have continued to attempt to develop the ELISA technique measure antibody against a variety of etiological agents which may be associated with multiple sclerosis or other neurological diseases. We have found that the ELISA technique is as adequate as existing serological tests to determine antibody titers but in most cases although the antibody titers are higher, the specificity of the tests are not much greater. Routine monitoring of cultures from experimental viral studies for mycoplasma contamination and efforts to develop new techniques to monitor tissue cultures for contamination have been continued.